Skip to main content

Full text of "Technology Study - Electric Arc Furnace Fume Systems and Control Technologies"

See other formats

py p\6S ^^O-^e^KHBP 



Electric Arc Furnace Fume Systems 


Control Technologies 

Expert Fume System Optimization Process - EFSOP^ 

CO, Hg 

I T' l i Ji Mi 

O2, CH4 

Ministry of the Environment 

ISBN 0-7778-6892-X 


Electric Arc Furnace Fume Systems 


Control Technologies 


Cette publication technique 
n'est disponible qu'en anglais. 

Copyright: Queen's Printer for Ontario, 1997 

This publication may be reproduced for non-commercial purposes 

with appropriate attribution. 

PIBS 3602E 


This report was prepared for the Ontario Ministry of the Environment as part of the ministry's 
information transfer activities. We hope that the report will provide perspective and encourage 
discussion in a rapidly changing technological world. The views expressed in this report are 
based on interpretations of various referenced authors and do not necessarily reflect 
the position or policies of the Ministry of the Environment and Energy, nor does mention of 
trade names or commercial products constitute endorsements or recommendation for use. 

Any person who wishes to republish part or all of this report should apply for permission to do 
so to the Environmental Technology Services Section, Industry Conservation Branch, Ontario 
Ministry of the Environment, 2 St. Clair Ave. W., 14th floor, Toronto, Ontario, 
M4V 1L5. 


The author would like to thank Dr. Howard Goodfellow (Goodfellow Consultants Inc.), 
Professor Alex McLean, (Chair, Department of Metallurgy and Materials Science, University 
of Toronto), and John Guerard (Process Metallurgist, Co-Steel Lasco), for their assistance in 
providing technical reviews of this report. This report would not have been possible without 
their essential contributions. 

Electric Arc Furnace Fume Systems and Control Technologies 


1. Introduction 1 

2. The History of EAF Developments 1 

3. Electric Arc Furnace Operation Overview 4 

4. EAF Emissions 4 

5. EAF Emission Capture Technology 5 

6. EAF Emission Control Technology 7 

7. EAF Emission Control Developments 7 

8. Innovations in Electric Arc Furnace Operations 7 

8.1 Scrap Preheating 7 

8.1.1 Batch Preheaters 8 

8.1.2 Continuous Preheaters 9 

8.2 Post-Combustion Technologies 9 

8.3 The Expert Fume System Optimization Process (EFSOP) 10 

9. The Ontario EAF Market H 

10. Barriers to Technology 13 

11. Emerging Trends 13 

12. Summary 1^ 

13. References 15 

Environmental Technology Services 

Electric Arc Furnace Fume Systems and Control Technologies 


Figure 1 . Influence of arc furnace technology on the main operating 

parameters of EAFs 3 


Table 1. Estimated particulate emission factors 5 

Table 2. Heat content in preheated steel scrap 8 

Table 3. Electric arc furnace operation in Ontario 12 


EAF Electric Arc Furnace 

ACFM Actual Cubic Feet per Minute 

DEC Direct Evacuation Control 

EFSOP Expert Fume System Optimization Process 

DRI Direct Reduced Iron 

Environmental Technology Services 


Electric Arc Furnace Fume Systems and Control Technologies 


Electric Arc Furnaces have been used in North America to make steel since 1906. Although 
imcommon at first, EAF melt shops have since steadily increased their share of the steelmaking 
market as companies have developed their expertise and increased production. The share of 
the steel market produced by EAFs grew from 19 per cent in 1976 to 36 per cent in 1986, and 
should reach 50 per cent by the year 2000* •^. 

Systems to control emissions from steehnaking have always been needed and particularly so 
with the advent of more stringent environmental regulations in recent years. 

However EAF fume systems have only lately been viewed as an opportunity to save energy 
and improve the steelmaking process. Steelmakers are now more aware of how an emission 
control system which is well designed and maintained can protect the environment and improve 
the productivity of their operations. 

This report highlights the technological improvements in EAF operations which have resulted 
in modem fume control technologies and which are the basis for future developments. 


The Heroult company in France introduced the EAF in 1899. The technology has since 
developed from being a slow process into a rapid melting machine that performs at a level 
which approaches that of the basic oxygen furnace. 

In the 1950s EAFs were small and usually located in a back comer of the melt shop. 
Emissions were relatively low and were of little concem to the steelmaker. The emissions 
were simply collected by fume hoods which were located above the furnace. 

However to ensure that the fume system operated properly, the associated duct work had to 
be telescoped or detached and cleaned during the steel pouring operation. This made the 
steelmaking process cumbersome. The solution was to eliminate the hoods and attach the duct 
work to the so-called fourth hole in the furnace roof. This represented the first form of a 
primary fiime control system. 

From 1965 to 1969 several primary EAF fume control systems were installed in the United 
States. Unformnately the hot gases at the fourth hole caused considerable problems in the duct 
work. This problem with the original designs was later solved by using water-cooled ducts to 
reduce the temperature of the gases. 

In the United Kingdom many gas collection systems were based on electrostatic precipitators 
that used conditioning towers to improve gas cleaning efficiency. Several facilities tried to use 
scrubber technology, but these were difficult to maintain and were deemed to be unreliable. 

Enviroimiental Technology Services 1 

Electric Arc Furnace Fume Systems and Control Technologies 

In order to improve the steelmaking process, oxygen was introduced into the furnace. 
This increased the amount of exhaust gases and dust and occasionally caused an explosion. 

These problems prompted the British Iron and Steel Federation to study the problem of air 
pollution from EAFs. In April of 1963 their report on the "Safe Treatment of Waste Gases" 
recommended that waste gases should be burned in a combustion box under controlled 

In response the British Steel Corporation (BSC) developed a combustion chamber for use in all 
of the company's EAF steel plants. The chamber was a refractory-lined cylinder which 
measured approximately 2.1 m in diameter and 3.4 m long. The combustion air was injected 
perpendicularly to the furnace off-gas flow through three radial tubes at the inlet to the 
combustion chamber. The after burners were located in two positions down stream from the 
injection of combustion air and were fuelled by natural gas or propane. 

Many EAF fume systems were installed in the United States in the early 1970s. However little 
or no development work was done to establish optimal designs. Most systems were based on 
experience and by copying previous installations, and deficiencies were simply corrected as 
they became apparent. 

One example of this approach was a fume control system based on direct evacuation which was 
installed by Laclede Steel in 1965*. By 1969 it was recognized that the equipment needed to be 
significantly modified to improve its fume collection capabilities. The plant had to construct a 
1 . 1 million ACFM DEC/canopy system which cost more than $5 million. 

In the United Kingdom, most melt shops because of their different shop geometries and 
melting practices installed similar pilot hoods as those used in the United States. In 1971 a test 
program to measure plume density and flow rates was started at the melt shop of BSC in 
Templeborough. As a result of these tests, the hoods and off-takes were modified and a 
statistical analysis program was developed to establish optimum control for melt shops with 
many furnaces. 

In 1976, Marchand^ with BFI in Diisseldorf concentrated his efforts on improving the dust 
collection systems in the EAF melt shops in Germany. He evaluated different layouts and 
different roof off-take configurations in melt shops that used enclosed furnaces. 

Substantial developments in fume control systems were made in the 1980s. These included 
furnace enclosures and the application of evaporative cooling to peak shaving for ultra-high- 
power furnaces. To improve heat transfer and reduce maintenance costs, new designs for 
water-cooled ducts were developed. New computer design programs also evolved to assist in 
the sizing of the DEC systems and canopy hoods. 

These and other technical improvements have decreased tap-to-tap times and reduced electricity 
use and electrode consumption (Figure 1). 

Environmental Technology Services 2 

Electric Arc Furnace Fume Systems and Control Technologies 

Figure 1 Influence of arc fiimace technology on the main operating parameters of EAFs''. 



Secondary (todie) metalurgy | 



Water-csoM wafc | 

— ^- 


High pMrflttooo vcoperatiofl 

— ^- 

Computer control 

— ^- 


Foaming slag practice 

yAteter-cootod rootroxy-fciel burner 

1 ^ 


Bottom taphote 


EBT (slag Itm) 

— ^> 

Sciap preheaUng 




\ \ \^ 

Higher po«ver electrk: supply 







Oxygen and caftion lance nnanipulalon 




/\ \v \ 




Tap-to-tap time y^ ^^\ ^\ 

Pneumatte bain simng 




/^^^\ ^^^\ ^^^^~-. ' ^ 









Electricity consumption ^^^ ^^--^^ ^"~-^^^^^ 

^▼^ ^^"-^^^ ^"~^^^„^^ ^"~^ 60 mm 
Electrode consumption ^^^^^ ^■'■^-.^ 

^^^^^ ^^ 410kV*/t 

— 2.2kgrt 


! i 

5 70 75 80 85 90 


Environmental Technology Services 

Electric Arc Furnace Fume Systems and Control Technologies 


The four major steps in scrap based EAF steel production are: 

• scrap handling and preparation; 

• melting and refining; 

• casting; and 

• rolling. 

The first step is the sorting and shredding of the scrap. The shredded scrap is then moved by 
rail or truck to the scrap bay in the meU shop building. 

The melt shop houses the EAF. The scrap is charged into the furnace along with carbon, lime 
and other additives. The primary energy source for the furnace is electricity, but significant 
amounts of hydrocarbon gas and oxygen are also used. Once the scrap has been melted, the 
molten metal is tapped into large refractory lined mobile vessels which are known as ladles. 
The chemistry of the molten metal is adjusted to meet specifications at the ladle furnace. 

The third step in the process is the caster where the liquid metal is poured from the ladle into a 
copper mold which is cooled by water. The solid metal which is produced is referred to as a 
billet, bloom, slab or round, depending on the size and shape of the cast product. 

The final part of an EAF steel plant is the rolling mill. The cast product is shaped to meet 
customer specifications by passing it between rolls which revolve in opposite directions. 
The shaped steel is then sent to market. 


All phases of operation at a steehnaking plant produce emissions. These emissions are 
categorized as primary if they are created during melting and refining, or as secondary if 
they occur during charging, tapping, slagging and other activities. 

Iron oxide is the main component of emissions from the EAF. Iron oxide has a highly visible 
red to grey colour and a high percentage of particles which are less than 2 microns in diameter. 
Since die goal of every steel plant is to emit dust-free discharges to the atmosphere, highly 
efficient gas cleaning equipment is required. 

Primary fume emissions can range from 7.5 to 20 kg of dust/tonne of hot metal tapped. 
The level of dust in the discharge depends on the cleanliness of the initial scrap, the amount 
of oxygen used, the quality of the lime, the power input level, the size of the fume system and 
the method of charge addition. 

Environmental Technology Services 

Electric Arc Furnace Fume Systems and Control Technologies 

Secondary fume emissions can be as low as 0.5 kg or as much as 3.5 kg of dust generated per 
tonne of hot metal tapped. The amount of dust depends on the quality of the scrap, the number 
of back charges, the adequacy of the fume system, the duration of the tap, the type of furnace 
and the quality of the ladle additions. 

Some estimates of particulate emission factors for a 100 per cent scrap metal shop and a DRI 
melt shop are provided below (Table 1). This information can be used to establish the level of 
fume control which is necessary to achieve specific rates of particulate emissions and meet 
requirements for opacity. 

Table 1 

Estimated particulate emission factors 

Type of 


100 Per Cent Scrap Melt 


DRI Melt Shop 

Particulate Emission 
Factor' Ob/ton of hot 

% Total 

Particulate Emission 
Factor* Ob/ton of hot 

% Total 


Leakage around 






















' Factors estimated by Goodfellow (1985)'. 



Since the EAF was invented, numerous technologies have been developed to capture the fumes 
which are generated by the steelmaking process. As the EAF process has improved so has the 
need to improve these techniques for fume capture. 

Early fume control systems were based on full hoods which were designed to capmre all the 
emissions from the steelmaking process. Over time and with improvements in the steehnaking 
process, improved emission controls were needed. In 1981 the Environmental Protection 
Agency published an article on "Electric Arc Furnaces and Argon-Oxygen Decarburization 
Vessels in Steel Plants - Background Information for Promulgated Standards" which described 
some of the technical features of the different types of fiune collection systems. 

At the Iron and Steel Society 1975 Electric Furnace Conference, Bruce Steiner of the American 
Iron and Steel Institute described seven different combinations of possible fume systems that 
can be used to control primary and secondary emissions. Most are based on the fourth hole 
DEC or roof canopy systems. A brief description of the more common systems follows. 

Enviroimiental Technology Services 

Electric Arc Furnace Fume Systems and Control Technologies 

The fourth hole DEC system works by evacuating the furnace through the associated duct work 
which feeds the gas cleaning equipment. The emission gases are cooled by diluting them with 
air and using water cooled ducts. The capacity of a DEC system is typically 1,000 Nnf/hour 
per tonne of furnace capacity. 

However fourth hole DEC systems do not always operate as designed. For example, changes 
in furnace pressure due to bath reactions and oxygen feeding occasionally cause fumes to 
escape through doors, ports, roof-sidewall joints and electrode openings, bypassing the DEC 
system. The DEC system also does not collect the fumes which are generated by the process 
when the EAF roof is open during charging and tapping. These fumes escape to the roof of 
the building and pose an environmental hazard if they are not collected. 

Many other EAF operations utilize a deep rectangular canopy hood over the furnace to capmre 
the fumes generated during charging, tapping, melting and refining. The canopy hood must be 
located so that the movements of any overhead cranes and other operations in the melt shop are 
not impeded. 

The effectiveness of canopy hoods is greatly increased if they have a large storage capacity. 
This greatly reduces the risk of fiigitive emissions being released into the atmosphere. 
The drawback of canopy hoods is that they cost more to install and operate. These types of 
systems typically have capacities of 340,000 to 850,000 Nnf /hour per furnace. 

Both the fourth hole DEC and roof canopy systems have certain disadvantages. However the 
two systems are substantially more effective when they are combined. Dampers and adequate 
controls are also necessary to ensure proper collection of fumes under different furnace 
operating conditions. 

Total shop evacuation is another available system. In this process the entire building is sealed 
and the fumes from the EAF are collected and filtered before the exhaust air is released to the 
atmosphere. A disadvantage of a total shop evacuation system is the extremely high capital, 
operating and maintenance costs. This type of evacuation system also must have enough 
capacity to exhaust all EAF fumes. Otherwise working conditions for the plant employees will 
deteriorate. The capacity of this type of system usually ranges from 2 to 3.4 million 

Furnace enclosures are a recent innovation in fume system design. Furnace enclosures seal in 
all the fumes which are generated by the EAF and then exhaust the fiimes through filters. 
This system typically needs less capacity than other fume control systems and this lowers the 
capital and operating costs. The DEC/canopy system for example requires 2.5 times more 
capacity than the furnace enclosure and the shop evacuation system requires 8 times more 
capacity. A further advantage of the furnace enclosure is that it substantially reduces noise 
emissions from an EAF. 

Environmental Technology Services 

Electric Arc Furnace Fume Systems and Control Technologies 


Three types of technologies are currently used for fume control at EAF plants; high-energy 
scrubbers, electrostatic precipitators and fabric filters. 

Scrubbers were originally used in small EAFs and they worked reasonably well. However as 
the furnaces got bigger it was necessary to move to high-energy scrubbers. Electrostatic 
precipitators were installed in a few plants but they were expensive and inefficient. Fabric 
filters are now preferred in over 95 per cent of the plants in North America, Europe and Japan. 


About 95 per cent of the EAF market use DEC/canopy hood systems. Traditionally such 
systems are designed to accommodate the peak heat load and volume requirements based on 
the most intense period of furnace practice. The system operates at this peak level for the 
entire heating period and this leads to a high heat loss from the furnace. 

Systems used today are also usually operating at capacities above that for which they were 
designed. Hence, there are numerous plants with inadequate DEC/canopy hood strucmres. 


Steelmakers are constantly striving to improve the steelmaking process. Recently several 
processes and technologies have emerged that enable steelmakers to increase their production 
rates and also to minimize the effect of the steelmaking process on the environment. 

8.1 Scrap Preheating 

Substantial electric energy can be saved by preheating scrap prior to charging. This techniques 
was first practised by the Japanese and the European steelmakers in the 1970s and the process 
has recently been adopted by some American steelmakers looking to improve their productivity 
and reduce their energy use. One major drawback of the preheating of scrap is the 
environmental problems which are associated with the transport of the preheated scrap to the 
EAF. The preheated scrap may still contain other semi-burned materials such as plastics 
which can be environmentally hazardous. Many of the systems in Europe have stopped using 
preheated scrap due to this concern, but technologies and processes have been developed to 
address the problem. 

Steelmakers that use preheating of scrap report savings between 30 and 70 kWh/tonne of liquid 
steel '^ Charging heated scrap to the furnace reduces the total heating time and reduces the tap 
to tap times. This lowers power consumption and extends the life of the electrode. Other 

Environmental Technology Services 

Electric Arc Furnace Fume Systems and Control Technologies 

benefits of preheated scrap are reduced shop noise and emissions, and the ability to charge oily 

Roughly 75 per cent of the total energ\' used in the EAF is to heat scrap. The balance of the 
energy goes into melting the solid scrap (approximately 20 per cent) and superheating the 
liquid to tapping temperature (5 per cent)'^ Typically electrical energy provides the majority 
of the energy. However over the last 30 years the EAF has become multi-fuelled to improve 
heating efficiency, with the supplemental energ>' from oxygen injection and oxy-fuel burners. 
The heat content of the preheated scrap depends on its temperature (Table 2), and this heat 
reduces the energy needed from other sources. 

Table 2 

Heat content in preheated steel scrap 


Scrap Temperature 

Heat Content (k\Mi/t) 

1 SOOT (150°C) 

22 1 

500T (260°C) 


TOOT (370°C) 


lOOOT (540°C) 


Scrap preheating operations can be continuous or batch processes and can use external heating 
sources, waste gas heating, or a combination of both. 

8.1.1 Batch Preheaters 

T\"pical batch preheaters are refractor)' lined buckets where the scrap is heated before it is 
charged to the furnace. 

External Heating Sources 

In this process the scrap is preheated by an external source such as a fuel-fired burner. It is 
important to closely monitor the results of this process. The steelmaker needs to be sure that 
the savings from increased production and reduced consumption of power by the furnace offset 
the cost of the external heating. Otherwise the process is not economically feasible. This 
method has been successfully implemented at Bethlehem Steel since 1971, Harrison Steel 
Castings and recently at Washington Steel'^. 

Waste Gas Heating 

The heat from waste gas. which would normally be lost to the environment, can be used to 
preheat the scrap. The installation at Badische Stahlwerke in Germany uses this technique. 
The waste eas heat from the furnace is collected through the fourth hole of the furnace and the 

Environmental Technology' Services 

Electric Arc Furnace Fume Systems and Control Technologies 

heat is forced through the scrap using water-cooled ducts and fans. Other locations which have 
successfully used waste gas heating are DDS in Denmark, which uses the Fuch's shaft furnace, 
Knoxville Iron Co., and Timken in Canton, Ohio'". 

8.1.2 Continuous Preheaters 

In continuous preheating systems, the scrap travels on a conveyor into the preheater. 
The conveyor may be vibrating, rotating kiln or gravity feed type. 

Waste Gas Heating 

EMPCO has developed the Verticon process'" for continuous pre-heating of scrap using waste 
gases. In this technique the charged scrap is held in a heated vessel which is located above the 
EAF furnace. The full heat charge for the furnace is contained in the vessel and is 
continuously charged after preheating. The off-gases from the furnace are collected and 
directed into the vessel for further incineration and preheating of scrap. 

Combination Waste & External Heating 

The BBC/Brusa process used in Italy uses waste gases from the furnace and heat from burning 
supplemental fuel to preheat the scrap'". The charged scrap is fed through an inclined 
revolving kiln which is heated by the waste gases from the furnace. The scrap is also further 
heated by gas-fired burners before it leaves the kiln. 

The Consteel process developed by Intersteel Technology Inc. in the USA is another type of 
continuous process that uses a covered conveyor type preheater. The system is made up of a 
charging conveyor for scrap, a feeding system to introduce carbon and fluxes, and a preheater. 
The preheated scrap is taken from the scrap preheater to the EAF via a connecting car. 

8.2 Post-Combustion Technologies 

Underbath oxygen lancing is the standard practice used in electric steeknaking since the early 
1960s. During lancing the carbon is partially oxidized to CO which is used to heat scrap in 
the EAF. Unfominately a large amount of the chemical energy of this process is lost as the 
furnace gases are exhausted to the fume system. 

The addition of oxygen during the post-combustion process to convert CO into CC^ allows 
much of this chemical energy to be recovered. Post-combustion is the most cost effective 
means available to supply energy to the furnace and to increase its productivity. The amount 
of oxygen used in EAF operations has steadily risen from 2 to 17.5 Nnf/ton of steel over the 
last 20 years'^ 

Praxair has used their expertise and experience to develop equipment and practices for efficient 
post-combustion in the EAF at Nucor's melt shop in Plymouth, Utah. The tests at Nucor 

Environmental Technology Services 

Electric Arc Furnace Fume Systems and Control Technologies 

involved three components: off-gas analysis, post-combustion with burners, and post- 
combustion with PC-lances'^. 

L'Air Liquid has also had some success in developing and implementing their ALARC PC 
process with allows for the efficient recovery of chemical energy in the off-gases. The system 
was installed at Vallourec St. Saulve Steelworks with the objective to increase productivity. 
The installation has reported a decrease in tap-to-tap time of 4 minutes and a reduction in 
electricity consimiption of 43 kWh/tonne". 

8.3 The Expert Fume System Optimization Process (EFSOP)" 

Goodfellow Consultants Inc. of Mississauga, Ontario, has developed a technology to control 
and optimize the operation of the EAF fume system. The EFSOP system continuously 
analyses the emissions, measures flow and temperature and monitors real-time process data in 
order to adjust fume system set points and operation on a minute-by-minute basis. 

The EFSOP system provides on-line measurements in real-time of what is occurring as the 
furnace emissions are exhausted. An added advantage is that the system can be used to control 
post-combustion systems. This optimizes furnace combustion, increases production and saves 
energy. Steelmakers have reported energy savings of 20 kWh/ton of steel and tap-to-tap time 
reductions of 2 to 3 minutes with EFSOP. 

Where plants are operating with inadequate DEC/canopy hood systems, EFSOP can quantify 
the amount of heat being released to the DEC system and determine what shortfalls exist in the 
system. Specific upgrades can then be identified. 

The EFSOP system analyses the furnace off-gas just before the combustion gap to quantify 
the amount of carbon monoxide (CO) in the off-gas. The CO results from the incomplete 
combustion of oxygen and fuel in the fiimace shell. Some furnace practices and scrap mixes 
also cause high levels of hydrogen (Hj) in the off-gas streams. Together, these combustible 
gases can make up over 30 per cent of the furnace off-gas and they represent a tremendous loss 
of energy. 

This loss and the high temperature of the off-gas can mean a waste of more than 2,000,000 
BTU/min (over 500 kWh/min) at peak points in the melts. This represents over 50 per cent of 
the electrical energy used by the furnace. As well as CO and H^, oxygen and carbon dioxide 
are measured in the gas sample. The flow and temperamre of the off-gas stream and process 
parameters from the furnace operating system also are monitored to give a complete real-time 
picture of the inputs and outputs of the process. 

The EFSOP system allows the steelmaker to mne the operation of the DEC system to match 
the acmal requirements of the process. The continuous fume analysis of the furnace off-gas 
allows the steelmaker to conduct controlled post-combustion and to capmre some of the energy 

Environmental Technology Services 10 

Electric Arc Furnace Fume Systems and Control Technologies 

that is being lost in the off-gas in the furnace, before it escapes into the DEC system. 

Once profiles of the off-gas have been established, alternative practices to optimize the 
operation of the furnace can be evaluated. This makes it possible to set operating parameters 
for the fume system which match the existing and anticipated heat load profiles. By 
monitoring process data from existing furnace control systems, these set points can be adjusted 
in real-time to match the actual furnace practice and to accommodate process upsets. 

The EFSOP technology has been used at a major Canadian steelmaker for several months and 
the data has yielded some valuable information such as: 

• the CO and Hj levels in the off-gas are significant for long periods of the heat. 
Maximum CO levels can exceed 25 per cent while maximum I^ levels can be more 
than 20 per cent; 

• measurements are highly variable which indicates that the process is complex and that 
many factors interact to affect the off-gas chemistry; and 

• the furnace loses significant amounts of heat while the system is idle. 

A post-combustion strategy is presently being evaluated and a control strategy for the DEC is 
also being developed at this facility. It is conservatively estimated that such a control strategy 
could save more than $1,000,000 each year. Note that steehnaking practices differ between 
EAF facilities and the control strategy for each plant must be individually developed. 


Steel is produced in Ontario at integrated mills that use the Blast Furnace-Basic Oxygen 
Furnace process and in mini-mills that use Electric Arc Furnaces. There are currently 7 EAF 
mini-mills operating in the province; Atlas Specialty Steels, Courtice Steel Inc., Co-Steel 
Lasco, Dominion Castings Ltd., Port Hope Foundry, Ivaco Rolling Mills Ltd. Partnership, and 
Slater Industries Inc. In addition to these, Dofasco which is an integrated plant has also 
recently installed an Electric Furnace facility. Each mini-mill operation is outlined in Table 3. 

The EAF melt shops in Ontario all operate a DEC and/or canopy hood type of system. The 
fume systems for these plants were all designed based on original fiimace practice intensities. 

Steehnakers in Ontario are increasing their production through improved technologies such as 
oxy-fiiel burners, oxygen lances, foamy slag practice, carbon injection and the addition of DRI 
and iron carbide. These improvements to the EAF have significantly increased the intensity of 
their EAF operations. For example the tap to tap times have decreased from 180 minutes in 
1965 to less than 60 minutes in 1990^. This has placed considerable stress on fume systems 
which have not substantially changed over the years. 

Environmental Technology Services 11 

















■3 K 

a 5 



CiJ ^ ;^- 


1" = 


X s. 



o c — 
= g 2 
< g 2 

b .= — 
= 3 S 

n y V 

< 1^ E 



o ", 








Q (J ± 

s g-.s 


1 = 

" s * 

■— . .S' ™ 

5 ^ go 

< 3 



















Electric Arc Furnace Fume Systems and Control Technologies 


EAF steelmaking operations continue to face more stringent regulations on emissions from the 
melt shop and for contaminant levels in the workplace. For example the new particulate 
regulation for the EAF requires that emissions from the melt shop are less than 6 per cent 
opacity^. This would mean that the melt shop can never have visible emissions. The primary 
and secondary fume collection system at an EAF facility will need to perform much better than 
previously to comply with these regulations. 

Other new regulations may reduce the acceptable levels in the workplace of metals such as lead 
and cadmium. Fumre designs of cost-effective fume control and ventilation systems for steel 
plants must account for these stricter requirements. 


The main issues that will dominate future developments with EAF operations are the 
availability of capital, productivity, energy efficiency and environmental concerns. Successful 
steelmakers will have to use the best available technologies and methods to integrate gains in 
productivity with improvements in energy efficiency and compliance with environmental 

The problem for many steelmakers is that they cannot afford to abandon their existing 
equipment or facilities. They must add and adapt improvements in technology to their existing 
EAFs. However it is important to ensure that the proper engineering is performed in order to 
determine the impacts on the overall operation. To increasing productivity without properly 
considering the impact on the fume control operations often results in existing fume systems 
being overloaded. 

Emerging technologies will focus on meeting the following objectives: 

• adoption of new scientific methods for the design of EAFs; the design of fume systems 
will be integrated with the furnace steelmaking practice and will no longer be based on 
empirical equations and rule of thumb practices. 

• incorporation of continuous fume analysis into melt shop practice; the trend will be to 
equip all fume systems with analyzers that will characterize the flow and composition of 
the off-gas. 

• limiting the amount of dust produced; more stringent environmental regulations mean 
that dust particles must be more effectively captured. 

Environmental Technology Services 13 

Electric Arc Furnace Fume Systems and Control Technologies 

moving towards the implementation of enclosed EAFs; the advantages in noise 
attenuation, higher productivity levels and reduced air pollution may encourage steel 
mills to adopt furnace enclosures. 

installing expert fume control systems; expert systems can be used on-line to operate 
EAF fume systems to optimize performance and improve the overall operation of the 


Electric Arc Furnace fume systems represent an opportunity to save energy and improve the 
steelmaking process. An emission control system which is well designed and maintained can 
protect the environment and improve the productivity of a steelmaking operation. Some of 
these opportunities and advances in technology which are discussed in this report include: 

• improvements in steehnaking practices have caused fume systems to become overloaded 
and the majority of fume systems are operating at a level beyond that for which they 
were designed. The development of technologies for analysis and control means that 
the fume system can now be operated to closely match the operation of the EAF, which 
minimizes the use of the fimie system and conserves energy. 

• expert fume analysis systems will increasingly be used to evaluate the fume system 
operations and the EAF practices at steel mills. 

• computer analysis systems and computer modelling systems will enable existing and 
new EAF plants to modify current and design new fume systems that will meet the 
increased heat load profiles at EAF plants while saving energy. 

• expert fume systems will allow the steelmaker to more closely control post-combustion 

• improvements in productivity, energy use and emissions to the environment may 
encourage steel mills to utilize enclosed EAFs. 

Environmental Technology Services 14 

Electric Arc Furnace Fume Systems and Control Technologies 


1. J.J. Bosley, Techno-Economic Assessment of Electric Steelmaking Through the year 
2000 . EPRI Centre for Metal Production, Research Project 2787-2, October 1987. 

2. H.D. Goodfellow, A pplication of Variable Speed Fans to Electric Arc Furnace Fume 
Systems . Air Pollution Control Specialty Conference, October 9-11, 1990. 

3. Research and Development Department, Stelco Inc.. Present and Future Use of Energy 
in the Canadian Steel Industry . Efficiency and Alternative Energy Technology Branch, 
CANMET, Energy, Mines and Resources Canada, Ottawa, Ontario, March 1993. 

4. H.D. Goodfellow, Fume Control for EAFs - Past. Present and Fumre . 12th Process 
Technology Conference, Part HI: Environmental Concerns in EAF Steelmaking, 
Washington DC, November 1993. 

5. Air Pollution from Electric Arc Furnaces: Safe Treatment of Gases . British Iron and 
Steel Federation, April 1963. 

6. R.A. Garvey, Design and Installation of Fume Control Svstem During Operations . 
Electric Furnace Proceedings, ISS, Vol. 33, Houston, TX, 1975, pp.26-29. 

7. D. Marchand, Possible Improvements to Dust Collection in Electric Ste elplants and 
Summary of All Planned and Existing Collection Systems in the Federal Republic of 
Germany . Ironmaking and Steelmaking, 1976, pp. 22 1-229. 

8. R.W. Manten, P.G.A. Brand, A Practical Primer on Design of EAF Emission Control 
Systems . Hatch Associates, Mississauga, 1994. 

9. Elsevier Science, H.D. Goodfellow, Advanced Design of Ventilation Sy stems for 
Contaminant Control . Amsterdam, 1985, pp. 416-419. 

10. H.D. Goodfellow, The Expert Fume System Optimization Process . News Release, 
Mississauga, Ontario, Nov. 1995. 

11. Electric Arc Furnace Roundup - Canada . Iron and Steelmaker, Annual Report, May 

12. Aristide Jean et al. The 90' s Electric Arc Furnace Steelm aking Route: The Leap 
Forward . Proceedings of the Sixth International Iron and Steel Congress, Nogoya, 
1990, pp. 180-189. 

13. C. Baukal, M. Lanyi, D. Winchester, Scrap Prehea ting with a Submersed Oxveen-Fuel 
Burner . ISS Spring Conference, Detroit, MI, 1990. 

Environmental Technology Services 15 

Electric Arc Furnace Fume Systems and Control Technologies 

14. Donald E. Klessen, Overview of Scrap Preheating . Centre for Materials Research, 
1991 Electric Furnace Conference Proceedings, pp. 67-69. 

15. The Electric Arc Furnace - 1990 . International Iron and Steel Institute, Belgium, 1990. 

16. Pravin Mathur, Giffm Daughtridge, Oxygen Injection for Effective Post-Combustion in 
the EAF . 51" Electric Furnace Conference Proceedings, Nov. 7-10, 1993. 

17. Industrial Practice of a New Injection Process of L'Air Liquide for Post-Combustion at 
Vallourec Saint-Sauve . 

Environmental Technology Services 16 


Electric Arc Furnace Fume Systems and Control Technologies 


We value your comments. By completing this form you will help us increase our understanding of how we 
can best utilize valuable resources and provide more useful information. 

1. Did you find this report of value to your business or operation? 

2. What part of the report did you find most useful? 

3. Are there technical or economic issues and opportunities not identified in the report? If so please identify. 

4. Are there areas in the report we can improve*? 

5 Any other comments you wish to share? 

Respondent's name/organizationyaddress/phone number: 

Please return a copy of this Reader Response Form by Fax or by mail to the following address: 

Ontario Ministry of the Environment 
Industry Conservation Branch 
2 St. Clair Avenue West, 14th Floor 
Toronto, Ontario, M4V ILS 

Tel: (416) 327-1253 
Fax: (416) 327-1261 

Attn. Gabriela Teodosiu 

For additional copies of this report please contact the Industry Conservation Branch.